1. Technical Field
The present invention relates to a photographing lens assembly. More to particularly, the present invention relates to a compact photographing lens assembly applicable to electronic products.
2. Description of Related Art
In recent years, with the popularity of mobile products with camera functionalities, the demand of miniaturized optical lens systems is increasing. The sensor of a conventional photographing camera is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical lens systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical lens systems featuring better image quality.
Most of the conventional compact lens systems adopt a two-lens element structure for cutting down the manufacturing cost, such as the optical lens system with two-lens element structure disclosed in U.S. Pat. No. 7,525,741 B1. However, as the optical lens system only has two lens elements, the aberration correction ability of the system is limited, and the system fails to satisfy higher imaging demands. On the other hand, other conventional optical lens systems with four-element lens structure such as the one disclosed in U.S. Pat. No. 8,039,704 B2 are provided. However, a compact size thereof is limited by the number of the lens elements, and the manufacturing costs rise relatively as the manufacturing and assembling processes are more complicated and difficult.
U.S. Pat. No. 7,397,612 B2 provides an optical lens system with three-element lens structure which comprises, in order from an object side to an image side, a first lens element with negative refractive power, a second lens element with positive refractive power, and a third lens element with positive refractive power. Although the field of view can be increased by such an optical lens system, the back focal length is also increased. The total track of length is thereby too long and therefore is not applicable to compact electronic products. Since the surface curvatures have limited ability in correcting the aberration and distortion, it is thereby not favorable for the imaging quality. Besides, the conventional optical lens systems are not suitable to be applied to the infrared photography, since these systems cannot be applied to detect infrared rays at night under the circumstance of insufficient light source or to capture the dynamic images.